The invention is directed to an arrangement for actuating dot-producing printing elements of a mosaic printing head, employing piezoelectric transducers which may be set in elongated or contracted states upon the application of suitable electric fields by means of electrical circuit arrangements, whereby, on the transition from the contracted state into the elongated state, the dot-producing printing elements are accelerated and the dot-producing printing element associated therewith, as a result of its own mass inertia, is moved towards the printing position. Subsequently, as a result of resetting energy (rebound and spring energy), the dot-producing element is returned from the printing position into its initial position.
It is generally known to operate individual dot-producing printing elements of mosaic printing heads by means of electromagnet systems. It has also been proposed to employ piezoelectric transducers for operation of such dot-producing printing elements, with the mosaic printing heads being so designed that the ends of the dot-producing printing elements, remote from the printing position, are urged by spring elements against flat, elongated piezoelectric transducers. In such case, the spring elements are so dimensioned that the applied spring forces are considerably lower than the forces acting upon the dot-producing printing elements during the elongation of the piezoelectric transducers, as a result of corresponding changes in the electric fields applied to the latter. In a mosaic printing head of such design, the advantages derived are that the drive means, i.e. the piezoelectric transducers can be arranged in very close relation and thus staggered or spaced in accordance with the pattern of the dot-producing printing elements. The overall dimensions of the printing head are thereby considerably reduced in comparison to conventional magnet drive means for dot-producing printing elements, and thus a corresponding reduction is achieved in the space required for the arrangement, as well as in the masses which are to be moved, accelerated and decelerated, and thus of the type carrier carriage which moves along the printing line during the printing operation.
In all printing operations in which the printing elements travel in free flight to the printing position, a fundamental difficulty exists with respect to the return of the printing elements, away from the printing position, into their initial position with the least possible vibration, in order to be available for the next operating sequence. It will be apparent that the more rapidly each printing element returns from the printing position into its initial rest position, the more quickly the next printing cycle can be initiated. Consequently, by shortening the vibration time, it is possible to considerably increase the printing speed.